Lesions of the laterodorsal tegmental nucleus disrupt prepulse inhibition of the acoustic startle reflex.

The purpose of the present studies was to determine the effects of bilateral lesions of the laterodorsal tegmental nucleus (LDTg) on prepulse inhibition (PPI) of the acoustic startle reflex under conditions of varying prepulse intensity and interstimulus interval (ISI) durations. Rats with bilateral ibotenic acid lesions of the LDTg were evaluated for changes in PPI and startle amplitude in comparison with an unoperated group, sham-LDTg lesioned group and a group with bilateral ibotenic acid lesions of the subcoeruleus nucleus, a brainstem nucleus approximately 1 mm ventrolateral to the LDTg. Bilateral lesions of the LDTg produced a robust decrease in PPI with no effect on startle amplitude as compared with the three control groups. In contrast, bilateral lesions of the subcoeruleus produced no effect on either PPI or startle amplitude. The effects of bilateral lesions of the LDTg on PPI were observed across prepulse intensities of 5, 10 and 15 dB above background and ISI durations of 30, 100, 300 and 1000 ms without significantly decreasing startle amplitude in either test paradigm as compared with the sham-LDTg lesioned group. Our data provide evidence for a role of the LDTg in modulating PPI.